Improvements in a gas powered engine. Said improvements include use of a piston with a fixed piston arm that extends through a seal in the lower portion of the cylinder. The piston arm operates on an elliptical crank that drives the output shaft. Valves that move air and exhaust into and out of the pistons are lifted by a cam located on the crank. A unique oil injector passes oil to the piston and the cylinder wall. An energy recovery unit recovers energy from the cooling system and from the exhaust system.